I have built a multiplexer which has 16 selectable analogue inputs and one analogue output which goes to one of the Bitalino channels. The 16 inputs to the multiplexer are connected on at a time all controlled by a counter which cycles eg 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,1,2,3,4,5.... etc.
The counter is a 4 bit binary counter so each bit is connected to the 4 bit Bitalino digital input. So if the counter is on count 0011 then the analogue signal on channel 3 is connected to the Bitalino analogue input. Bitalino sampling at 1kHz so each of the 16 analogue inputs needs to have a max frequency of 15Hz or resolution can be lost, with less channels the frequency would be higher but this works with slowly varying analogue such as a bicycle where pedal rotation, gear rotation, brake application, steering input etc. can be recorded along with the other Bitalino channels of ECG + EMG. The processing of the Excel data file is fairly easy to extract the 16 discrete signals.